Ice age

Variations in temperature, CO₂, and dust from the Vostok, Antarctica ice core over the last 400,000 years

File:20191021 Temperature from 20,000 to 10,000 years ago - recovery from ice age.png

Rise of temperature at the end of the last ice age

An ice age is a period that for a long time the temperature of Earth's climate is very low. That leads to an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.

'Ice age' is a term used in palaeoclimatology for the period of extensive ice sheets in the recent Pleistocene period. We now know that ice ages have happened a number of times in the past, the greatest and longest of which took place in the Proterozoic era, before multicellular eukaryotes evolved.^[1]^[2]

During ice ages, the sea level drops as water is held in the great ice sheets at the poles. How much it drops depends on several factors, such as the length of time that a cold period lasts.

Stages

Within an ice age, there are stages. The longer cold stages are called glacials or glacial periods. The shorter warm periods are called interglacials. The last glacial ended about 11,000 years ago, when the present interglacial started. The Greenland and Antarctic ice sheets still exist. The last two million years have been the Pleistocene ice age. During glacials, large and thick ice sheets covered much of North America and Eurasia.

Many glacial periods that have occurred during the last few million years are initially at 40,000-year frequency, but more recently ice ages have occurred at 100,000-year frequency.

This data come from a time that human beings had no large effect on the climate. Therefore, it is technically correct to say that humans had no effect on global climate in the Earth's history. However, in recent centuries they have burned much fossil fuel, which has partly been responsible for the present temperature rise.

Ice Age Media

IceAgeEarth.jpg

An artist's impression of ice age Earth at Pleistocene glacial maximum
AntarcticaDomeCSnow.jpg

The Antarctic ice sheet. Ice sheets expand during an ice age.
Haukalivatnet.JPG

Haukalivatnet lake (50 meters above sea level) where Jens Esmark in 1823 discovered similarities to moraines near existing glaciers in the high mountains
GlaciationsinEarthExistancelicenced annotated.jpg

Timeline of glaciations, shown in blue
EisrandlagenNorddeutschland.png

Ice age map of northern Germany and its northern neighbours. Red: maximum limit of Weichselian glacial; yellow: Saale glacial at maximum (Drenthe stage); blue: Elster glacial maximum glaciation.
Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years
Ice Age Temperature.png

Shows the pattern of temperature and ice volume changes associated with recent glacials and interglacials.
Diagram of key climate-carbon cycle feedbacks linking Quaternary climates and temperatures, Generalized Milankovitch Theory (GMT), to atmospheric CO₂ and ice sheets. Positive feedbacks amplify and negative feedbacks dampen environmental change, with slow-acting responses shown as dashed arrows.
SummerSolstice65N-future.png

Past and future of daily average insolation at top of the atmosphere on the day of the summer solstice, at 65 N latitude

Related pages

References

↑ Imbrie J. & Imbri, K.P. 1979. Ice ages: solving the mystery. Short Hills NJ: Enslow. ISBN 978-0-89490-015-0
↑ Alley R.B. 2000. The two-mile time machine: ice cores, abrupt climate change, and our future. Princeton University Press. ISBN 0-691-10296-1

Other websites

Cracking the Ice Age from PBS
Climate patterns^{[dead link]}

[1] Imbrie J. & Imbri, K.P. 1979. Ice ages: solving the mystery. Short Hills NJ: Enslow. ISBN 978-0-89490-015-0

[2] Alley R.B. 2000. The two-mile time machine: ice cores, abrupt climate change, and our future. Princeton University Press. ISBN 0-691-10296-1

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